/*
 * This program implements the
 * Proposed Federal Information Processing
 *  Data Encryption Standard.
 * See Federal Register, March 17, 1975 (40FR12134)
 */

/*
 * Initial permutation,
 */
static char    IP[] = {
       58,50,42,34,26,18,10, 2,
       60,52,44,36,28,20,12, 4,
       62,54,46,38,30,22,14, 6,
       64,56,48,40,32,24,16, 8,
       57,49,41,33,25,17, 9, 1,
       59,51,43,35,27,19,11, 3,
       61,53,45,37,29,21,13, 5,
       63,55,47,39,31,23,15, 7,
};

/*
 * Final permutation, FP = IP^(-1)
 */
static char    FP[] = {
       40, 8,48,16,56,24,64,32,
       39, 7,47,15,55,23,63,31,
       38, 6,46,14,54,22,62,30,
       37, 5,45,13,53,21,61,29,
       36, 4,44,12,52,20,60,28,
       35, 3,43,11,51,19,59,27,
       34, 2,42,10,50,18,58,26,
       33, 1,41, 9,49,17,57,25,
};

/*
 * Permuted-choice 1 from the key bits
 * to yield C and D.
 * Note that bits 8,16... are left out:
 * They are intended for a parity check.
 */
static char    PC1_C[] = {
       57,49,41,33,25,17, 9,
        1,58,50,42,34,26,18,
       10, 2,59,51,43,35,27,
       19,11, 3,60,52,44,36,
};

static char    PC1_D[] = {
       63,55,47,39,31,23,15,
        7,62,54,46,38,30,22,
       14, 6,61,53,45,37,29,
       21,13, 5,28,20,12, 4,
};

/*
 * Sequence of shifts used for the key schedule.
*/
static char    shifts[] = {
       1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1,
};

/*
 * Permuted-choice 2, to pick out the bits from
 * the CD array that generate the key schedule.
 */
static char    PC2_C[] = {
       14,17,11,24, 1, 5,
        3,28,15, 6,21,10,
       23,19,12, 4,26, 8,
       16, 7,27,20,13, 2,
};

static char    PC2_D[] = {
       41,52,31,37,47,55,
       30,40,51,45,33,48,
       44,49,39,56,34,53,
       46,42,50,36,29,32,
};

/*
 * The C and D arrays used to calculate the key schedule.
 */

static char    C[28];
static char    D[28];

/*
 * The key schedule.
 * Generated from the key.
 */
static char    KS[16][48];

/*
 * The E bit-selection table.
 */
static char    E[48];
static char    e[] = {
       32, 1, 2, 3, 4, 5,
        4, 5, 6, 7, 8, 9,
        8, 9,10,11,12,13,
       12,13,14,15,16,17,
       16,17,18,19,20,21,
       20,21,22,23,24,25,
       24,25,26,27,28,29,
       28,29,30,31,32, 1,
};

/*
 * Set up the key schedule from the key.
 */

static
setkey(key)
char *key;
{
       int     i, j, k;
       int     t;
       char    *ptr;

       /*
        * First, generate C and D by permuting
        * the key.  The low order bit of each
        * 8-bit char is not used, so C and D are only 28
        * bits apiece.
        */
       for (i=0; i<28; i++) {
               C[i] = key[PC1_C[i]-1];
               D[i] = key[PC1_D[i]-1];
       }
       /*
        * To generate Ki, rotate C and D according
        * to schedule and pick up a permutation
        * using PC2.
        */
       for (i=0; i<16; i++) {
               /*
                * rotate.
                */
               for (k=0; k<shifts[i]; k++) {
                       t = C[0];
                       ptr = C;
                       for (j=0; j<28-1; j++)
                       {
                               *ptr = ptr[1];
                               ptr++;
                       }
                       C[27] = t;
                       t = D[0];
                       ptr = D;
                       for (j=0; j<28-1; j++)
                       {
                               *ptr = ptr[1];
                               ptr++;
                       }
                       D[27] = t;
               }
               /*
                * get Ki. Note C and D are concatenated.
                */
               ptr = &KS[i][0];
               for (j=0; j<24; j++) {
                       ptr[j] = C[PC2_C[j]-1];
                       ptr[j+24] = D[PC2_D[j]-28-1];
               }
       }

       for(i=0;i<48;i++)
               E[i] = e[i];
}

/*
 * The 8 selection functions.
 * For some reason, they give a 0-origin
 * index, unlike everything else.
 */
static char    S[8][64] = {
       14, 4,13, 1, 2,15,11, 8, 3,10, 6,12, 5, 9, 0, 7,
        0,15, 7, 4,14, 2,13, 1,10, 6,12,11, 9, 5, 3, 8,
        4, 1,14, 8,13, 6, 2,11,15,12, 9, 7, 3,10, 5, 0,
       15,12, 8, 2, 4, 9, 1, 7, 5,11, 3,14,10, 0, 6,13,

       15, 1, 8,14, 6,11, 3, 4, 9, 7, 2,13,12, 0, 5,10,
        3,13, 4, 7,15, 2, 8,14,12, 0, 1,10, 6, 9,11, 5,
        0,14, 7,11,10, 4,13, 1, 5, 8,12, 6, 9, 3, 2,15,
       13, 8,10, 1, 3,15, 4, 2,11, 6, 7,12, 0, 5,14, 9,

       10, 0, 9,14, 6, 3,15, 5, 1,13,12, 7,11, 4, 2, 8,
       13, 7, 0, 9, 3, 4, 6,10, 2, 8, 5,14,12,11,15, 1,
       13, 6, 4, 9, 8,15, 3, 0,11, 1, 2,12, 5,10,14, 7,
        1,10,13, 0, 6, 9, 8, 7, 4,15,14, 3,11, 5, 2,12,

        7,13,14, 3, 0, 6, 9,10, 1, 2, 8, 5,11,12, 4,15,
       13, 8,11, 5, 6,15, 0, 3, 4, 7, 2,12, 1,10,14, 9,
       10, 6, 9, 0,12,11, 7,13,15, 1, 3,14, 5, 2, 8, 4,
        3,15, 0, 6,10, 1,13, 8, 9, 4, 5,11,12, 7, 2,14,

        2,12, 4, 1, 7,10,11, 6, 8, 5, 3,15,13, 0,14, 9,
       14,11, 2,12, 4, 7,13, 1, 5, 0,15,10, 3, 9, 8, 6,
        4, 2, 1,11,10,13, 7, 8,15, 9,12, 5, 6, 3, 0,14,
       11, 8,12, 7, 1,14, 2,13, 6,15, 0, 9,10, 4, 5, 3,

       12, 1,10,15, 9, 2, 6, 8, 0,13, 3, 4,14, 7, 5,11,
       10,15, 4, 2, 7,12, 9, 5, 6, 1,13,14, 0,11, 3, 8,
        9,14,15, 5, 2, 8,12, 3, 7, 0, 4,10, 1,13,11, 6,
        4, 3, 2,12, 9, 5,15,10,11,14, 1, 7, 6, 0, 8,13,

        4,11, 2,14,15, 0, 8,13, 3,12, 9, 7, 5,10, 6, 1,
       13, 0,11, 7, 4, 9, 1,10,14, 3, 5,12, 2,15, 8, 6,
        1, 4,11,13,12, 3, 7,14,10,15, 6, 8, 0, 5, 9, 2,
        6,11,13, 8, 1, 4,10, 7, 9, 5, 0,15,14, 2, 3,12,

       13, 2, 8, 4, 6,15,11, 1,10, 9, 3,14, 5, 0,12, 7,
        1,15,13, 8,10, 3, 7, 4,12, 5, 6,11, 0,14, 9, 2,
        7,11, 4, 1, 9,12,14, 2, 0, 6,10,13,15, 3, 5, 8,
        2, 1,14, 7, 4,10, 8,13,15,12, 9, 0, 3, 5, 6,11,
};

/*
 * P is a permutation on the selected combination
 * of the current L and key.
 */
static char    P[] = {
       16, 7,20,21,
       29,12,28,17,
        1,15,23,26,
        5,18,31,10,
        2, 8,24,14,
       32,27, 3, 9,
       19,13,30, 6,
       22,11, 4,25,
};

/*
 * The current block, divided into 2 halves.
 */

static char    L[64];
#define R   (L + 32)
static char    tempL[32];
static char    f[32];

/*
 * The combination of the key and the input, before selection.
 */
static char    preS[48];

/*
 * The payoff: encrypt a block.
 */

static
encrypt (block, edflag)
char *block;
{
       int i, ii;
       register t, j, k;

       /*
        * First, permute the bits in the input
        */
       for (j=0; j<64; j++)
               L[j] = block[IP[j]-1];
       /*
        * Perform an encryption operation 16 times.
        */
       for (ii=0; ii<16; ii++) {
/*             print_bits ("L R", L); */
               /*
                * Set direction
                */
               if (edflag)
                       i = 15-ii;
               else
                       i = ii;
               /*
                * Save the R array,
                * which will be the new L.
                */
               for (j=0; j<32; j++)
                       tempL[j] = R[j];
               /*
                * Expand R to 48 bits using the E selector;
                * exclusive-or with the current key bits.
                */
               for (j=0; j<48; j++)
                       preS[j] = R[E[j]-1] ^ KS[i][j];
               /*
                * The pre-select bits are now considered
                * in 8 groups of 6 bits each.
                * The 8 selection functions map these
                * 6-bit quantities into 4-bit quantities
                * and the results permuted
                * to make an f(R, K).
                * The indexing into the selection functions
                * is peculiar; it could be simplified by
                * rewriting the tables.
                */
               for (j=0; j<8; j++) {
                       t = 6*j;
                       k = S[j][(preS[t+0]<<5)+
                               (preS[t+1]<<3)+
                               (preS[t+2]<<2)+
                               (preS[t+3]<<1)+
                               (preS[t+4]<<0)+
                               (preS[t+5]<<4)];
                       t = 4*j;
                       f[t+0] = (k>>3)&01;
                       f[t+1] = (k>>2)&01;
                       f[t+2] = (k>>1)&01;
                       f[t+3] = (k>>0)&01;
               }
               /*
                * The new R is L ^ f(R, K).
                * The f here has to be permuted first, though.
                */
               for (j=0; j<32; j++)
                       R[j] = L[j] ^ f[P[j]-1];
               /*
                * Finally, the new L (the original R)
                * is copied back.
                */
               for (j=0; j<32; j++)
                       L[j] = tempL[j];
       }
       /*
        * The output L and R are reversed.
        */
       for (j=0; j<32; j++) {
               t = L[j];
               L[j] = R[j];
               R[j] = t;
       }
       /*
        * The final output
        * gets the inverse permutation of the very original.
        */
       for (j=0; j<64; j++)
               block[j] = L[FP[j]-1];
}

static
bytes_to_bits (bytes, bits)
    unsigned char   *bytes;
    char           *bits;
{
    int            bit, byte, value;

    for (byte = 0; byte < 8; byte++)
    {
       value = *bytes++;
       for (bit = 0; bit < 8; bit++)
           *bits++ = (value >> (7-bit)) & 1;
    }
}

static
bits_to_bytes (bits, bytes)
    char           *bits;
    unsigned char   *bytes;
{
    int            bit, byte, value;

    for (byte = 0; byte < 8; byte++)
    {
       value = 0;
       for (bit = 0; bit < 8; bit++)
           value |= *bits++ << (7-bit);
       *bytes++ = value;
    }
}

/*
 * Interface compatible with Kerberos DES implementation
 */

# include   "Wrap.h"

/*ARGSUSED*/
_XdmcpAuthSetup (key, schedule)
    auth_cblock                key;
    auth_wrapper_schedule      schedule;
{
    char    expand_key[64];

    bytes_to_bits ((unsigned char *) key, expand_key);
    setkey (expand_key);
}

/*ARGSUSED*/
_XdmcpAuthDoIt (input, output, schedule, edflag)
    auth_cblock                input, output;
    auth_wrapper_schedule      schedule;
    int                        edflag;
{
    char    expand_input[64];

    bytes_to_bits ((unsigned char *) input, expand_input);
    encrypt (expand_input, !edflag);
    bits_to_bytes (expand_input, (unsigned char *) output);
}
